Objective: To investigate the effect of cytokine-induced killer cells (CIK) combined with mFOLFOX6 regimen (fluorouracil+oxaliplatin+calcium folinate) on advanced colorectal cancer. Methods: 161 patients with advanced colon cancer admitted to the Fourth Clinical College of Xinxiang Medical College, Xinxiang Central Hospital of Henan Province from 2019 to 2021 were selected and divided into the study group (mFOLFOX6 regimen chemotherapy+CIK therapy) with 80 cases and the control group (mFOLFOX6 regimen chemotherapy) with 81 cases. The KPS score, median survival time, progression-free survival time, the proportion of Treg in peripheral blood mononuclear cells, the levels of CD4+, CD4+/CD8+, the expression levels of Foxp3 and CD127 mRNA, the quality-of-life score and the occurrence of toxic and side effects were compared between the two groups before and after chemotherapy. Results: The ages of patients in the study group and the control group were (64.8±7.5) and (66.1±7.0) years old, respectively, and the proportions of males were 62.5% (50 cases) and 50.6% (41 cases), respectively (both P values>0.05). After 2 cycles of chemotherapy and at the end of chemotherapy, the proportions of Treg, Foxp3 and CD127 mRNA in the study group were lower than those in the control group [2 cycles of chemotherapy: (4.33±0.86)% vs (4.89±1.20)%, (0.61±0.22) vs (0.73±0.20), (0.58±0.13) vs (0.70±0.15); after chemotherapy: (2.66±0.70)% vs (3.31±0.84)%, (0.43±0.18) vs (0.51±0.16), (0.41±0.10) vs (0.50±0.13)] (all P values<0.05). The KPS scores of the study group were higher than those of the control group [2 cycles of chemotherapy: (68.41±5.41) points vs (65.38±5.11) points; after chemotherapy: (72.08±5.94) points vs (67.95±5.51) points] (all P values<0.05). The median survival time of the study group was (16.8±2.2) months, which was higher than that of the control group [(11.2±1.8) months]. The progression-free survival time of the study group was also higher than that of the control group [(9.5±1.1) months vs (6.4±1.2) months], and the mortality rate was lower than that of the control group [11.3% (9 cases) vs 31.3% (25 cases)] (all P values<0.001). After chemotherapy, the scores of physical function, emotional function and role function in the study group were higher than those in the control group, and the scores of pains, fatigue and insomnia in the study group were lower than those in the control group (all P values<0.05). Conclusions: CIK combined with mFOLFOX6 regimen for advanced colorectal cancer can improve and regulate the immune function of patients, prolong the survival time of patients, and enhance the quality of life of patients.